Smartphone-assisted colorimetric sensor coupled with magnetically recoverable MnFe2O4/ZnO/rGO nanocomposites for trace detection and photocatalytic removal of tetracycline antibiotics.

In this work, a MnFe2O4/ZnO/rGO nanocomposite was successfully synthesized and explored for dual applications in photocatalytic degradation and colorimetric detection of tetracycline (TC) antibiotics. The structural, optical, and morphological analyses confirmed the formation of well-integrated heterostructures, featuring enhanced interfacial interactions and efficient electron-transfer properties. The MnFe2O4/ZnO/rGO nanocomposites exhibited excellent photocatalytic performance, achieving a degradation efficiency of 95.65% towards TC antibiotics under light irradiation, attributed to efficient charge separation and enhanced generation of ROS species. Additionally, the MnFe2O4/ZnO/rGO nanocomposites demonstrated strong peroxidase-like activity, enabling sensitive colorimetric detection of TC antibiotics via inhibition of TMB oxidation, with a linear response in the range of 10-90 μM and a low detection limit (LOD) of 0.21 μM. The MnFe2O4/ZnO/rGO nanocomposite system also showed high selectivity against interfering species and good reproducibility in real sample analysis, with recoveries ranging from 92.59 to 101.69%. Furthermore, a smartphone-based RGB analysis provided a simple, portable, and cost-effective detection strategy. This work highlights the potential of MnFe2O4/ZnO/rGO nanocomposites as a multifunctional platform for environmental monitoring and water remediation applications.